Antireflective coating compositions

ABSTRACT

Antireflective compositions are provided that contain an ionic thermal acid generator material. Use of such a thermal acid generator material can significantly increase the shelf life of solutions of antireflective compositions in protic media. Antireflective compositions of the invention can be effectively used at a variety of wavelengths used to expose an overcoated photoresist layer, including 248 nm and 193 nm.

This application claims the benefit of U.S. Provisional Application No.60/290,446 filing date May 11, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to compositions that reduce reflection ofexposing radiation from a substrate back into an overcoated photoresistlayer. More particularly, the invention relates to anti-reflectivecoating compositions that contains an ionic thermal acid generatorcompound. The compositions can exhibit, inter alia, enhanced storagestability.

2. Background

Photoresists are photosensitive films used for the transfer of images toa substrate. A coating layer of a photoresist is formed on a substrateand the photoresist layer is then exposed through a photomask to asource of activating radiation. The photomask has areas that are opaqueto activating radiation and other areas that are transparent toactivating radiation. Exposure to activating radiation provides aphotoinduced or chemical transformation of the photoresist coating tothereby transfer the pattern of the photomask to the photoresist-coatedsubstrate. Following exposure, the photoresist is developed to provide arelief image that permits selective processing of a substrate.

A photoresist can be either positive-acting or negative-acting. For mostnegative-acting photoresists, those coating layer portions that areexposed to activating radiation polymerize or crosslink in a reactionbetween a photoactive compound and polymerizable reagents of thephotoresist composition. Consequently, the exposed coating portions arerendered less soluble in a developer solution than unexposed portions.For a positive-acting photoresist, exposed portions are rendered moresoluble in a developer solution while areas not exposed remaincomparatively less soluble in the developer solution. Photoresistcompositions are described in Deforest, Photoresist Materials andProcesses, McGraw Hill Book Company, New York, ch. 2, 1975 and byMoreau, Semiconductor Lithography, Principles, Practices and Materials,Plenum Press, New York, ch. 2 and 4.

A major use of photoresists is in semiconductor manufacture where anobject is to convert a highly polished semiconductor slice, such assilicon or gallium arsenide, into a complex matrix of electronconducting paths, preferably of micron or submicron geometry, thatperform circuit functions. Proper photoresist processing is a key toattaining this object. While there is a strong interdependency among thevarious photoresist processing steps, exposure is believed to be one ofthe most important steps in attaining high resolution photoresistimages.

Reflection of activating radiation used to expose a photoresist oftenposes limits on resolution of the image patterned in the photoresistlayer. Reflection of radiation from the substrate/photoresist interfacecan produce spatial variations in the radiation intensity in thephotoresist, resulting in non-uniform photoresist linewidth upondevelopment. Radiation also can scatter from the substrate/photoresistinterface into regions of the photoresist where exposure is nonintended, again resulting in linewidth variations. The amount ofscattering and reflection will typically vary from region to region,resulting in further linewidth non-uniformity. Variations in substratetopography also can give rise to resolution-limiting problems.

One approach used to reduce the problem of reflected radiation has beenthe use of a radiation absorbing layer interposed between the substratesurface and the photoresist coating layer. See for example, PCTApplication WO 90/03598, EPO Application No. 0 639 941 A1 and U.S. Pat.Nos. 4,910,122, 4370,405, 4,362,809, and 5,939,236. Such layers havealso been referred to as antireflective layers or antireflectivecompositions. See also U.S. Pat. Nos. 5,939,236; 5,886,102; 5,851,738;and 5,851,730, all assigned to the Shipley Company, which disclosehighly usefull antireflective compositions.

SUMMARY OF THE INVENTION

We have now discovered new antireflective compositions for use with anovercoated photoresist layer that can exhibit enhanced properties,including enhanced storage stability (i.e. shelf life stability).

We have found that certain antireflective compositions can exhibitlimited shelf life, e.g. produce particles or become turbid duringstorage and prior to use. More particularly, certain anti-reflectivecoating compositions include a thermal acid generator or an acid thatlimit the shelf life of the composition. Without being bound by theory,it is believed that interaction between antireflective compositioncomponents can result in less than desirable shelf life.

We have discovered that use of an ionic thermal acid generator compoundcan significantly enhance the storage stability of an organic solventantireflective composition. Exemplary ionic thermal acid generatorsinclude e.g. sulfonate salts, preferably arylsulfonate salts such astoluenesulfonate acid amine salt.

Antireflective compositions of the invention suitably comprise a resinand a thermal acid generator (TAG). Preferred antireflectivecompositions of the invention contain a crosslinking component, and theantireflective composition is crosslinked prior to applying aphotoresist composition layer over the antireflective composition layer.An antireflective composition may contain an oligiomeric or polymericthermal acid generator as the sole resin component of an antireflectivecomposition. It is generally preferred however that an antireflectivecomposition contain at least one resin component in addition to anythermal acid generator component, e.g. to impart good film-formingproperties to the antireflective composition.

Antireflective compositions of the invention also will contain acomponent that comprises chromophore groups that can absorb undesiredradiation used to expose the overcoated resist layer from reflectingback into the resist layer. Generally preferred chromophores arearomatic groups, including both single ring and multiple ring aromaticgroups such as optionally substituted phenyl, optionally substitutednaphthyl, optionally substituted anthracenyl, optionally substitutedphenanthracenyl, optionally substituted quinolinyl, and the like.Particularly preferred chromophores may vary with the radiation employedto expose an overcoated resist layer. More specifically, for exposure ofan overcoated resist at 248 nm, optionally substituted anthracene is aparticularly preferred chromophore of the antireflective composition.For exposure of an overcoated resist at 193 nm, optionally substitutedphenyl is a particularly preferred chromophore of the antireflectivecomposition. Preferably, such chromophore groups are linked (e.g.pendant groups) to a resin component of the antireflective composition,either a polymeric thermal acid generator component or an additionalresin component distinct from the polymeric base additive.

As mentioned, preferred antireflective coating compositions of theinvention can be crosslinked, e.g. by thermal and/or radiationtreatment. For example, preferred antireflective coating compositions ofthe invention may contain a separate crosslinker component that cancrosslink with one ore more other components of the antireflectivecomposition. Generally preferred crosslinking antireflectivecompositions comprise a separate crosslinker component. Particularlypreferred antireflective compositions of the invention contain asseparate components: a resin, a crosslinker, and a thermal acidgenerator additive. Additionally, crosslinking antireflectivecompositions of the invention preferably can also contain an amine basicadditive to promote elimination of footing or notching of the overcoatedphotoresist layer. Crosslinking antireflective compositions arepreferably crosslinked prior to application of a photoresist layer overthe antireflective coating layer. Thermal-induced crosslinking of theantireflective composition by activation of the thermal acid generatoris generally preferred.

Antireflective compositions of the invention are typically formulatedand applied to a substrate as an organic solvent solution. A variety ofsolvents, including protic solvents such as ethyl lactate can beutilized to formulate an antireflective composition of the invention.

Antireflective compositions of the invention may be used with a varietyof overcoated photoresists. Preferred photoresists for use withantireflective compositions of the invention includechemically-amplified positive-acting photoresists, includingphotoresists that contain a component (typically a resin) that containsacetal or ketal groups (together referred to as acetal groups herein);ester groups such as t-butyl ester groups such as may be provided bypolymerization of t-butylacrylate, t-butyl methacrylate, methyladamantylacrylate, methyladamantyl methacrylate; and the like. Such resist resinsalso may contain other groups such as phenolic units which are preferredfor imaging at deep UV wavelengths (248 nm); or non-aromatic groups suchas polymerized optionally substituted norbornene, particularly forresists imaged with sub-200 nm radiation (e.g. 193 nm).

The invention further provides methods for forming a photoresist reliefimage and novel articles of manufacture comprising substrates (such as amicroelectronic wafer substrate) coated with an antireflectivecomposition of the invention alone or in combination with a photoresistcomposition. Additionally, the invention further provides stablesubstantially neutral solutions of antireflective compositions in proticmedia e.g. alcohols such as ethyl lactate for extended shelf life priorto use of the antireflective composition in forming an antireflectivecoating on a substrate. Other aspects of the invention are disclosedinfra.

DETAILED DESCRIPTION OF THE INVENTION

As discussed above, a substantially neutral or ionic thermal acidgenerator additive is stable for extended time periods in protic media.Preferably the substantially neutral thermal acid generator compositionis stable in protic media such as alcohols or water without generatingan acidic solution for 1 or 2 months or greater, more typically about 3,4, 5, 6, 7, 8 or 9 months or greater.

Without being bound by any theory, it is believed the use of an ionicthermal acid generator in an antireflective composition of the inventioncan inhibit undesired bleaching of the radiation-absorbing chromophoreemployed in the antireflective composition (e.g. anthracene for anantireflective composition imaged at 248 nm, phenyl for anantireflective composition imaged at 193 nm, and the like).

It is also believed that the cation component of the ionic thermal acidgenerator, particularly an amine-based anion, can provide beneficialeffects. More particularly, for a so-called low-temperature photoresistthat has an acetal resin, the thermally decomposed ionic thermal acidgenerator can help immobilize the thermally-generated acid in theantireflective composition coating layer. Such immobilization of thethermally-generated acid in the antireflective composition coating layeravoids migration of the acid into the overcoated photoresist layer. Suchundesired migration of the thermally-generated acid into the resistlayer can significantly compromise resolution of an image patterned inthe resist layer, e.g. the developed resist relief image can have anegative slope profile (undercutting), where the migrated thermally-acidresulted in undesired removal of non-exposed lower regions of the resistlayer.

In the case of so-called high temperature photoresists, e.g. resiststhat contain ester photoacid-labile groups such as polymerizedt-butylacrylate or t-butylmethacrylate units, use of a volatile amine asthe cation component for the thermal acid generator can providesignificant benefits. In such systems, the amine can be removed(volatized) from the antireflective composition coating layer duringthermal curing of that layer.

Preferred substantially neutral thermal acid generator additives containsulfonate salts, such as carbocyclic aryl (e.g. phenyl, napthyl,anthracenyl, etc.), heteroaryI (e.g. thienyl) or aliphatic sulfonatesalts, preferably carbocyclic aryl sulfonate salts. A thermal acidgenerator additive can be aromatic or non-aromatic. Preferred thermalacid generator additives contain optionally substituted benzenesulfonatesalts, preferably para-alkylbenzenesulfonate salts.

As indicated above, preferred thermal acid generator cations contain atleast one nitrogen. Preferred cations contain one or more optionallysubstituted amine groups. An amine-containing cation may contain one ormore primary, secondary, tertiary and/or quaternary ammonium groups.Preferred amine-containing cations have one or more amine groups with anactive proton, e.g. a primary, secondary and/or tertiary ammonium group.Substituents of an amine-containing cation of a thermal acid generatorsuitably may be e.g. optionally substituted alkyl such as optionallysubstituted C₁₋₁₂alkyl, optionally substituted aryl such as optionallysubstituted phenyl, naphthyl, anthracenyl, and the like; optionallysubstituted heteroalkyl such as optionally substituted C₁₋₁₂heteroalykl,particularly C₁₋₁₂alkoxy; etc.

Primary, secondary or tertiary aliphatic amines are particularlypreferred cation components of thermal acid generators used in ARCs ofthe invention. For example, cationic counter ions of substantiallyneutral thermal acid generator compounds of the invention include thoseof the formula [(R₁)(R₂)(R₃)NH]⁺, where R₁, R₂, and R₃ are independentlyhydrogen or an optionally substituted alkyl group such as optionallysubstituted C₁-C₁₆ alkyl, with at least one of R₁, R₂, and R₃ beingother than hydrogen.

Substituents of substituted carbocyclic aryl groups of ionic carbocyclicaryl sulfonate salts of the invention include e.g. hydroxy; optionallysubstituted alkyl e.g. alkyl having from 1 to about 16 carbon atoms,more typically alkyl having from 1 to about 8 carbon atoms; optionallysubstituted alkenyl e.g. alkenyl having from 2 to about 16 atoms, moretypically alkenyl having from 2 to about 8 atoms; optionally substitutedalknyl e.g. alkynyl having from 2 to about 16 atoms, more typicallyalkynyl having from 2 to about 8 carbon atoms; optionally substitutedalkoxy e.g. alkoxy having from 1 to about 16 atoms, more typicallyalkoxy having from 1 to about 8 atoms; optionally substitutedcarbocyclic aryl e.g. optionally substituted phenyl, optionallysubstituted naphthyl, optionally substituted anthracene and the like;optionally substituted aralkyl such as aralkyl having from 7 to about 20carbon atoms e.g. optionally substituted benzyl and the like; andoptionally substituted heteroaromatic or heteroalicyclic groupspreferably having 1 to 3 rings, 3 to 8 ring members in each ring andform 1 to 3 heteroatoms such as coumarinyl, quinolinyl, pyridyl,pyrazinyl, pyrimidyl, furyl, pyrrolyl, thienyl, thiazolyl, oxazolyl,imidazolyl, indolyl, benzofuranyl, benzothiazol, tetrahydrofuranyl,tetrahydropyranyl, piperdinyl, morpholino, and pyrrolindinyl; etc.Further there can be 1, 2, 3, 4 or 5 independently chosen substituentson the arene ring or more specifically, at each occurrence of an arenehydrogen substituent can be optionally replaced with an abovelistedsubstituent. Preferred arene groups have 0, 1 or 2 independently chosennon-hydrogen substituents.

As discussed above, lower molecular weight substantially neutral thermalacid generator additives can also be suitably employed in antireflectivecompositions of the invention, including non-polymeric substantiallyneutral thermal acid generator additives. For example, suitablesubstantially neutral thermal acid generator additives include thosehaving a molecular weight of less than about 600 daltons, more typicallyless than about 500, 400, 300, 200, or 150 daltons. A TAG additivetypically will have a molecular weight of at least 100, 125, 150 or 200daltons.

Preferred lower molecular weight ionic thermal acid generator additives,which may be non-polymeric, include substituted sulfonate ammoniumsalts, including ammonium or primary, secondary, and tertiary ammoniumsalts that may be substituted with e.g. groups specified above, i.e.hydroxy; optionally substituted alkyl; optionally substituted alkenyl;optionally substituted alkynyl; optionally substituted alkoxy;optionally substituted carbocyclic aryl; optionally substituted aralkyl;and optionally substituted heteroaromatic or heteroalicyclic groups;etc.

Ionic thermal acid generator compounds of the invention suitably mayhave a relatively high molecular weight. Such higher molecular weightmaterials will be less prone to volatilization during any thermal curingof an antireflective coating layer that contains the substantiallyneutral thermal acid generator compound. Preferred higher molecularweight substantially neutral thermal acid generator compounds have amolecular weight of at least about 100, 150, 200, 250, 300, 400, 500,600, 700, 800, 900, 1000 daltons. Even higher molecular weight additivesalso will be preferred such as substantially neutral thermal acidgenerator additives having a molecular weight of at least about 1200,1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, 3000, 3500, 4000, 4500,5000, 6000, 7000, 8000, 9000, 10000, 15000, 20000, 30000 daltons. Forpolymeric materials, molecular weight references herein are to Mw.

Oligiomeric and polymeric ionic thermal acid generator additives havingarylsulfonic acid salt substitutions either integral to the polymerbackbone or as pendant moieties. Suitable oligiomeric or polymericsulfonate salts of the antireflective compositions of the invention canbe formed by polymerization of two or more distinct monomers. Suchmonomers may be characterized as a sulfonated monomer if the monomercontributes to the neutral thermal acid generator nature of the polymer,or as a non-sulfonated monomer if the monomer does not contribute to theneutral thermal acid generator nature of the polymer. Based on thatnomenclature, preferred copolymer substantially neutral thermal acidgenerator additives comprise from about 1 to about 50 mole percentsulfonated monomers, more preferably from about 2 to about 20 molepercent sulfonated monomers, still more preferably from about 5 to about10 mole percent sulfonated monomers.

Alternatively, appropriate oligiomeric or polymeric sulfonate salts ofthe antireflective compositions of the invention may be prepared by apost-polymerization process that introduces sulfonic acid or sulfonatesalt groups into the polymer. Sulfonation reactions are well known inthe art and any suitable reaction that will introduce a sulfonate orsulfonic acid residue in the polymer is acceptable. Non-limitingexamples include sulfonation by treatment of a polymer or oligiomer withsulfuric acid, sulfur trioxide, and like sulfonation reagents. Based onthe above nomenclature, preferred post-polymerization sulfonatedsubstantially neutral thermal acid generator additives comprise fromabout 1 to about 50 mole percent sulfonated monomers, more preferablyfrom about 2 to about 20 mole percent sulfonated monomers, still morepreferably from about 5 to about 10 mole percent sulfonated monomers.

Crosslinking antireflective compositions of the invention preferablycomprise a substantially neutral thermal acid generator, e.g. anammonium arenesulfonate salt, for catalyzing or promoting crosslinkingduring curing of an antireflective composition coating layer. Typicallya non-polymeric or non-oligiomeric ionic thermal acid generator ispresent in an antireflective composition in a concentration from about0.1 to 10 percent by weight of the total of the dry components of thecomposition, more preferably about 2 percent by weight of the total drycomponents. Polymeric or oligiomeric substantially neutral thermal acidgenerators are present in the antireflective composition in aconcentration of from about 0.2 to about 20 percent by weight of thetotal of the dry components of the composition, more preferably fromabout 1 to about 5 percent by weight of the total dry components. Theconcentration of the polymeric or oligiomeric substantially neutralthermal acid generator is dependent upon the mole percent of sulfonatedmonomers in the polymeric additive e.g. for highly sulfonated polymeradditives, a lower by weight concentration of substantially neutralthermal acid generator is suitable.

As discussed above, antireflective compositions may suitablely contain aresin component in addition to the base additive material. Suitableresin components may contain chromophore units for absorbing radiationused to image an overcoated resist layer before undesired reflectionscan occur.

For deep UV applications (i.e. the overcoated resist is imaged with deepUV radiation), a polymer of an antireflective composition preferablywill absorb reflections in the deep UV range (typically from about 100to 300 nm). Thus, the polymer preferably contains units that are deep UVchromophores, i.e. units that absorb deep UV radiation. Highlyconjugated moieties are generally suitable chromophores. Aromaticgroups, particularly polycyclic hydrocarbon or heterocyclic units, aretypically preferred deep UV chromophore, e.g. groups having from two tothree to four fused or separate rings with 3 to 8 members in each ringand zero to three N, O or S atoms per ring. Such chromophores includeoptionally substituted phenanthryl, optionally substituted anthracyl,optionally substituted acridine, optionally substituted naphthyl,optionally substituted quinolinyl and ring-substituted quinolinyls suchas hydroxyquinolinyl groups. Optionally substituted anthracenyl groupsare particularly preferred for 248 nm imaging of an overcoated resist.Preferred antireflective composition resins have pendant anthracenegroups. Preferred resins include those of Formula I as disclosed on page4 of European Published Application 813114A2 of the Shipley Company.

Another preferred resin binder comprises optionally substitutedquinolinyl groups or a quinolinyl derivative that has one or more N, Oor S ring atoms such as a hydroxyquinolinyl. The polymer may containother units such as carboxy and/or alkyl ester units pendant from thepolymer backbone. A particularly preferred antireflective compositionresin in an acrylic containing such units, such as resins of formula IIdisclosed on pages 4-5 of European Published Application 813114A2 of theShipley Company.

For imaging at 193 nm, the antireflective composition preferably maycontain a resin that has phenyl chromophore units. For instance, onesuitable antireflective resin for use with photoresists imaged at 193 nmis a terpolymer consisting of polymerized units of styrene,2-hydroxyethylmethacrylate and methyhlethacrylate (30:38:32 mole ratio).Such phenyl group containing resins and use of same in antireflectivecompositions have been disclosed in U.S. application Ser. No.09/153,575, file 1998 and corresponding European Published ApplicationEP87600A1, assigned to the Shipley Company.

Preferably resins of antireflective compositions of the invention willhave a weight average molecular weight (Mw) of about 1,000 to about10,000,000 daltons, more typically about 5,000 to about 1,000,000daltons, and a number average molecular weight (Mn) of about 500 toabout 1,000,000 daltons. Molecular weights (either Mw or Mn) of thepolymers of the invention are suitably determined by gel permeationchromatography.

While antireflective composition resin binders having such absorbingchromophores are generally preferred, antireflective compositions of theinvention may comprise other resins either as a co-resin or as the soleresin binder component. For example, phenolics, e.g. poly(vinylphenols)and novolaks, may be employed. Such resins are disclosed in theincorporated European Application EP 542008 of the Shipley Company.Other resins described below as photoresist resin binders also could beemployed in resin binder components of antireflective compositions ofthe invention.

The concentration of such a resin component of the antireflectivecompositions of the invention may vary within relatively broad ranges,and in general the resin binder is employed in a concentration of fromabout 50 to 95 weight percent of the total of the dry components of theantireflective composition, more typically from about 60 to 90 weightpercent of the total dry components (all components except solventcarrier).

Crosslinking-type antireflective compositions of the invention alsocontain a crosslinker component. A variety of crosslinkers may beemployed, including those antireflective composition crosslinkersdisclosed in Shipley European Application 542008 incorporated herein byreference. For example, suitable antireflective composition crosslinkersinclude amine-based crosslinkers such as melamine materials, includingmelamine resins such as manufactured by American Cyanamid and sold underthe tradename of Cymel 300, 301, 303, 350, 370, 380, 1116 and 1130.Glycolurils are particularly preferred including glycolurils availablefrom American Cyanamid. Benzoquanamines and urea-based materials alsowill be suitable including resins such as the benzoquanamine resinsavailable from American Cyanamid under the name Cymel 1123 and 1125, andurea resins available from American Cyanamid under the names of Beetle60, 65, and 80. In addition to being commercially available, suchamine-based resins may be prepared e.g. by the reaction of acrylamide ormethacrylamide copolymers with formaldehyde in an alcohol-containingsolution, or alternatively by the copolymerization of N-alkoxymethylacrylamide or methacrylamide with other suitable monomers.

Suitable substantially neutral crosslinkers include hydroxy compounds,particularly polyfunctional compounds such as phenyl or other aromaticshaving one or more hydroxy or hydroxy alkyl substitutents such as aC₁₋₈hydroxyalkyl substitutents. Phenol compounds are generally preferredsuch as di-methanolphenol (C₆H₃(CH₂OH)₂)H) and other compounds havingadjacent (within 1-2 ring atoms) hydroxy and hydroxyalkyl substitution,particularly phenyl or other aromatic compounds having one or moremethanol or other hydroxylalkyl ring substitutent and at least onehydroxy adjacent such hydroxyalkyl substituent.

It has been found that a substantially neutral crosslinker such as amethoxy methylated glycoluril used in antireflective compositions of theinvention can provide excellent lithographic performance properties,including significant reduction (SEM examination) of undercutting orfooting of an overcoated photoresist relief image.

A crosslinker component of antireflective compositions of the inventionin general is present in an amount of between about 5 and 50 weightpercent of total solids (all components except solvent carrier) of theantireflective composition, more typically in an amount of about 7 to 25weight percent total solids.

Antireflective compositions of the invention also may contain additionaldye compounds that absorb radiation used to expose an overcoatedphotoresist layer. Other optional additives include surface levelingagents, for example, the leveling agent available under the tradenameSilwet 7604 from Union Carbide, or the surfactant FC 171 or FC 431available from the 3M Company.

To make a liquid coating composition, the components of theantireflective composition are dissolved in a suitable solvent such as,for example, ethyl lactate or one or more of the glycol ethers such as2-methoxyethyl ether (diglyme), ethylene glycol monomethyl ether, andpropylene glycol monomethyl ether; solvents that have both ether andhydroxy moieties such as methoxy butanol, ethoxy butanol, methoxypropanol, and ethoxy propanol; esters such as methyl cellosolve acetate,ethyl cellosolve acetate, propylene glycol monomethyl ether acetate,dipropylene glycol monomethyl ether acetate and other solvents such asdibasic esters, propylene carbonate and gamma-butyro lactone. Theconcentration of the dry components in the solvent will depend onseveral factors such as the method of application. In general, thesolids content of an antireflective composition varies from about 0.5 to20 weight percent of the total weight of the antireflective composition,preferably the solids content varies from about 2 to 10 weight of theantireflective composition.

A variety of photoresist compositions can be employed with theantireflective compositions of the invention, including positive-actingand negative-acting photoacid-generating compositions. Photoresists usedwith antireflective compositions of the invention typically comprise aresin binder and a photoactive component, typically a photoacidgenerator compound. Preferably the photoresist resin binder hasfunctional groups that impart alkaline aqueous developability to theimaged resist composition.

As discussed above, particularly preferred photoresists for use withantireflective compositions of the invention are chemically-amplifiedresists, particularly positive-acting chemically-amplified resistcompositions, where the photoactivated acid in the resist layer inducesa deprotection-type reaction of one or more composition components tothereby provide solubility differentials between exposed and unexposedregions of the resist coating layer. A number of chemically-amplifiedresist compositions have been described, e.g., in U.S. Pat. Nos.4,968,581; 4,883,740; 4,810,613; 4,491,628 and 5,492,793, al of whichare incorporated herein by reference for their teaching of making andusing chemically amplified positive-acting resists.

As discussed above, antireflective compositions also are suitably usedwith positive chemically-amplified photoresists that have acetal groupsthat undergo deblocking in the presence of a photoacid. Suchacetal-based resists have been described in e.g. U.S. Pat. Nos.5,929,176 and 6,090,526.

The antireflective compositions of the invention also may be used withother positive resists, including those that contain resin binders thatcomprise polar functional groups such as hydroxyl or carboxylate and theresin binder is used in a resist composition in an amount sufficient torender the resist developable with an aqueous alkaline solution.Generally preferred resist resin binders are phenolic resins includingphenol aldehyde condensates known in the art as novolak resins, homo andcopolymers or alkenyl phenols and homo and copolymers ofN-hydroxyphenyl-maleimides.

Copolymers containing phenol and nonaromatic cyclic alcohol units arealso preferred resin binders for resists of the invention and may besuitably prepared by partial hydrogenation of a novolak orpoly(vinylphenol) resin. Such copolymers and the used thereof inphotoresist compositions are disclosed in U.S. Pat. No. 5,128,232 toThackeray et al.

Preferred negative-acting resist compositions for use with anantireflective composition of the invention comprise a mixture ofmaterials that will cure, crosslink or harden upon exposure to acid, anda photoacid generator.

Particularly preferred negative-acting resist compositions comprise aresin binder such as a phenolic resin, a crosslinker component and aphotoactive component of the invention. Such compositions and the usethereof have been disclosed in European Patent Applications 0164248 and0232972 and in U.S. Pat. No. 5,128,232 to Thackeray et al. Preferredphenolic resins for use as the resin binder component include novolaksand poly(vinylphenol)s such as those discussed above. Preferredcrosslinkers include amine-based materials, including melamine,glycolurils, benzoguanamine-based materials and urea-based materials.Melamine-formaldehyde resins are generally most preferred. Suchcrosslinkers are commercially available, e.g. the melamine resins soldby American Cyanamid under the trade names Cymel 300, 301 and 303.Glycoluril resins are sold by American Cyanamid under trade names Cymel1170, 1171, 1172, Powderlink 1174, urea-based resins are sold under thetradenames of Beetle 60, 65 and 80, and benzoguanamine resins are soldunder the trade names of Cymel 1123 and 1125.

Suitable photoacid generator compounds of resists used withantireflective compositions of the invention include the onium salts,such as those disclosed in U.S. Pat. Nos. 4,442,197, 4,603,10, and4,624,912, each incorporated herein by reference; and non-ionic organicphotoactive compounds such as the halogenated photoactive compounds asin U.S. Pat. No. 5,128,232 to Thackeray et al. and sulfonate photoacidgenerators including sulfonated esters and sulfonlyoxy ketones. See J.of Photopolymer Science and Technology, 4(3):337-340 (1991), fordisclosure of suitable sulfonate PAGS, including benzoin tosylate,t-butylphenyl alpha-(p-toluenesulfonyloxy)-acetate and t-butylalpha(p-toluenesulfonyloxy)-acetate. Preferred sulfonate PAGs are alsodisclosed in U.S. Pat. No. 5,344,742 to Sinta et al. The abovecamphorsulfoanate PAGs 1 and 2 are also preferred photoacid generatorsfor resist compositions used with the antireflective compositions of theinvention, particularly chemically-amplified resists of the invention.

Photoresists for use with an antireflective composition of the inventionalso may contain other materials. For example, other optional additivesinclude actinic and contrast dyes, anti-striation agents, plasticizers,speed enhancers, etc. Such optional additives typically will be presentin minor concentration in a photoresist composition except for fillersand dyes which may be present in relatively large concentrations suchas, e.g., in amounts of from about 5 to 50 percent by weight of thetotal weight of a resist's dry components.

Antireflective compositions of the invention that include a low basicitycrosslinker such as a suitable glycoluril are particularly useful withphotoresists that generate a strong acid photoproduct upon exposure suchas triflic acid, camphor sulfonic acid, or other sulfonic acid, or otheracid having a pKa (25° C.) of about 2 or less. Without wishing to bebound by theory, it is believed that antireflective compositions of theinvention are particularly effective with such strong acid resistsbecause the strong photogenerated acid will migrate from the resist andremain in the antireflective composition layer to a lesser extentrelative to a comparable antireflective composition that contains a morebasic crosslinker. That is, the low basicity crosslinkers will tie upstrong photogenerated acids of an overcoated resist layer to a lesserextent than a more basic antireflective composition crosslinker. As aresult, less acid loss from the resist layer will occur and resolutionproblems such as footing will be even further reduced.

Various substituents and materials (including substantially neutralthermal acid generators, resins, etc.) as being “optionally substituted”may be suitably substituted at one or more available positions by e.g.halogen (F, Cl, Br, I); nitro; hydroxy; amino; alkyl such as C₁₋₈ alkyl;alkenyl such as C₂₋₈ alkenyl; alkylamino such as C₁₋₈ alkylamino;carbocyclic aryl such as phenyl, naphthyl, anthracenyl, etc; and thelike.

In use, an antireflective composition of the invention is applied as acoating layer to a substrate by any of a variety of methods such as spincoating. The antireflective composition in general is applied on asubstrate with a dried layer thickness of between about 0.02 and 0.5 μm,preferably a dried layer thickness of between about 0.04 and 0.20 μm.The substrate is suitably any substrate used in processes involvingphotoresists. For example, the substrate can be silicon, silicon dioxideor aluminum-aluminum oxide microelectronic wafers. Gallium arsenide,silicon carbide, ceramic, quartz or copper substrates may also beemployed. Substrates for liquid crystal display or other flat paneldisplay applications are also suitably employed, for example glasssubstrates, indium tin oxide coated substrates and the like. Substratesfor optical and optical-electronic devices (e.g. waveguides) also can beemployed.

Preferably the antireflective coating layer is cured before aphotoresist composition is applied over the antireflective composition.Cure conditions will vary with the components of the antireflectivecomposition. Particularly the cure temperature will depend on thespecific substantially neutral thermal acid generator. Typical cureconditions are from about 80° C. to 225° C. for about 0.5 to 40 minutes.Cure conditions preferably render the antireflective composition coatinglayer substantially insoluble to the photoresist solvent as well as analkaline aqueous developer solution.

After such curing, a photoresist is applied over the surface of theantireflective composition. As with application of the antireflectivecomposition, the photoresist can be applied by any standard means suchas by spinning, dipping, meniscus or roller coating. Followingapplication, the photoresist coating layer is typically dried by heatingto remove solvent preferably until the resist layer is tack free.Optimally, essentially no intermixing of the antireflective compositionlayer and photoresist layer should occur.

The resist layer is then imaged with activating radiation through a maskin a conventional manner. The exposure energy is sufficient toeffectively activate the photoactive component of the resist system toproduce a patterned image in the resist coating layer. Typically, theexposure energy ranges from about 3 to 300 mJ/cm² and depending in partupon the exposure tool and the particular resist and resist processingthat is employed. The exposed resist layer may be subjected to apost-exposure bake if desired to create or enhance solubilitydifferences between exposed and unexposed regions of a coating layer.For example, negative acid-hardening photoresists typically requirepost-exposure heating to induce the acid-promoted crosslinking reaction,and many chemically amplified positive-acting resists requirepost-exposure heating to induce an acid-promoted deprotection reaction.Typically post-exposure bake conditions include temperatures of about50° C. or greater, more specifically a temperature in the range of fromabout 50° C. to about 160° C.

The exposed resist coating layer is then developed, preferably with anaqueous based developer such as an alkali exemplified by tetra butylammonium hydroxide, sodium hydroxide, potassium hydroxide, sodiumcarbonate, sodium bicarbonate, sodium silicate, sodium metasilicate,aqueous ammonia or the like. Alternatively, organic developers can beused. In general, development is in accordance with art recognizedprocedures. Following development, a final bake of an acid-hardeningphotoresist is often employed at temperatures of from about 100° C. toabout 150° C. for several minutes to further cure the developed exposedcoating layer areas.

The developed substrate may then be selectively processed on thosesubstrate areas bared of photoresist, for example, chemically etching orplating substrate areas bared of photoresist in accordance withprocedures well known in the art. Suitable etchants include ahydrofluoric acid etching solution and a plasma gas etch such as anoxygen plasma etch. A plasma gas etch removes the crosslinkedantireflective coating layer.

All documents mentioned herein are incorporated herein by reference. Thefollowing non-limiting examples are illustrative of the invention.

EXAMPLE 1

Synthesis of ARC Polymer

An initial amount of 249 kg THF is charged to the 100 gallon reactorusing residual vacuum. 21.05 kg of 9 Anthracene Methyl Methacrylate(Antma) is added to reactor and mixed with THF until dissolved. Thepre-weighed quantities of 16.00 kg Methyl Methacrylate (MMA), 12.5 kg2-Hydroxyethyl Methacrylate (HEMA), and Vazo 65 free radical initiatorsolutions are added to the reactor. The reaction mixture is agitatedunder vacuum and purged with nitrogen three times to remove dissolvedoxygen. After the final nitrogen purging, the vessel is heated to areaction temperature of 66C and run at reflux temperature andatmospheric pressure for 30 hrs.

MTBE is used as the precipitation solvent and is charged via vacuum tothe precipitation vessel. When the reaction is complete and the batch iscooled down, it is transferred to the precipitation vessel in severalincrements for precipitation through a spray nozzle to form a slurry.The product is filtered out using a 48″ Hastelloy buchner funnel fittedwith a 10 μm polypro filter bag. The cake is washed with additionalMTBE. A dam is put on the filter cake on the Buchner Funnel and air ispassed over the filter cake to remove MTBE and dry the cake. PGME ischarged to a process vessel, and then the filter cake is charge to theprocess vessel for vacuum stripping of MTBE.

The finished product is drummed off as a 14-16% polymer solution inPGME.

All process equipment is washed with propylene glycol methyl ether(PGME), followed by Acetone. Plastic containers can be cleaned with THFafter use. About 200 gms of Phenothiazine inhibitor is added to theprocess filtrate of THF and MTBE to inhibit peroxide formation.

EXAMPLE 2

Reference ARC with Non-ionic TAG (Comparative)

An antireflective composition was prepared by dissolving together 0.7845g of the polymer of Example 1, 0.0990 g of Powderlink 1174 crosslinker(from Cytec Industries), 0.009 g of p-nitrobenzyltosylate thermal acidgenerator, 0.0072 g of FC 430 surfactant (3M Corp.) and 30.96 g ofproylene glycol methyl ether alcohol solvent. After dissolution, thesolution was filtered through a polyproylene filter with a 0.2 um poresize.

The filtered solution was then spin-cast on a 100 mm silicon wafer andthen baked at 175° C., to give a film thickness of about 600 angstroms.A popular commercially available “hybrid-acetal resist”, SE430 (ShinEtsu Corp.) was then spin coated on top of the antireflective film, andbaked at 90 C for 60 seconds to give a film thickness of 6000 angstroms.The resist was then exposed on a GCA 0.55 NA stepper using 248 nm lightthrough a mask to form a equal lines/spaces patterns of variousresolutions in the film. The resist film was then post-exposure baked at110 C/60 sec, and developed with 2.38% tetramethyl ammonium hydroxidedeveloper using a standard wafer-track single-puddle process.

The developed wafers were then inspected using a scanning electronmicroscope to determine the patterned fidelity. An exposure dose waschosen which gave a line/space pattern of equal size.

SE430 resist on the antireflective film of this composition gave poorpattern fidelity. The resist sidewalls were significantly undercut atthe resist/antiflective interface. At resolutions less than or equal too240 nm, the resist undercut was bad enough to cause complete patterncollapse.

This example illustrates the problems experienced with antireflectivecompositions containing non-ionic thermal acid generators.

EXAMPLE 3

Reference ARC Containing an Acidic Crosslinking Catalyst

An antireflective composition was prepared by dissolving together 0.7845g of the polymer of Example 1, 0.0990 g of Powderlink 1174 crosslinker(from Cytec Industries), an acid crosslinking catalyst consisting of0.009 g of p-toluene sulphonic acid monohydrate (Aldrich Corp.), 0.0072g of FC 430 surfactant (3M Corp.) and 30.96 g of proylene glycol methylether alcohol solvent. After dissolution, the solution was filteredthrough a polyproylene filter with a 0.2 um pore size.

The filtered solution was then spin-cast on a 100 mm silicon wafer andthen baked at 175° C., to give a film thickness of about 600 angstroms.A popular commercially available “hybrid-acetal resist”, SE430 (ShinEtsu Corp.) was then spin coated on top of the antireflective film, andbaked at 90 C for 60 seconds to give a film thickness of 6000 angstroms.The resist was then exposed on a GCA 0.55 NA stepper using 248 nm lightthrough a mask to form a equal lines/spaces patterns of variousresolutions in the film. The resist film was then post-exposure baked at110° C./60 sec, and developed with 2.38% tetramethyl ammonium hydroxidedeveloper using a standard wafer-track single-puddle process.

The developed wafers were then inspected using a scanning electronmicroscope to determine the patterned fidelity. An exposure dose waschosen which gave a line/space pattern of equal size.

The SE430 resist displayed a “bowed” resist sidewall appearance, with anundercut at the resist/antireflectant interface. The undercut was lessthan observed in Example 2.

EXAMPLE 4

ARC Using an Ionic Thermal Acid Generator

The thermal acid generator (TAG) evaluated in this example was Nacure5225, an amine salt of dodecylbenzene sulphonic acid.

An antireflective composition was prepared by dissolving together 0.7845g of the polymer of Example 1, 0.0990 g of Powderlink 1174 crosslinker(from Cytec Industries), an acid crosslinking catalyst consisting of0.009 g of Nacure 5225 (King Industries), 0.0072 g of FC 430 surfactant(3M Corp.) and 30.96 g of proylene glycol methyl ether alcohol solvent.After dissolution, the solution was filtered through a polyproylenefilter with a 0.2 um pore size.

The filtered solution was then spin-cast on a 100 mm silicon wafer andthen baked at 175° C., to give a film thickness of about 600 angstroms.A popular commercially available “hybrid-acetal resist”, SE430 (ShinEtsu Corp.) was then spin coated on top of the antireflective film, andbaked at 90° C. for 60 seconds to give a film thickness of 6000angstroms. The resist was then exposed on a GCA 0.55 NA stepper using248 nm light through a mask to form a equal lines/spaces patterns ofvarious resolutions in the film. The resist film was then post-exposurebaked at 110° C./60 seconds, and developed with 2.38% tetramethylammonium hydroxide developer using a standard wafer-track single-puddleprocess.

The developed wafers were then inspected using a scanning electronmicroscope to determine the patterned fidelity. An exposure dose waschosen which gave a line/space pattern of equal size.

The SE430 resist displayed a straight resist sidewall appearance, withno undercut or footing at the resist/antireflectant interface. Resistadhesion was excellent, with features of 200 nm resolution showing notendency to tip over.

EXAMPLE 5

ARC Using an Ionic Thermal Acid Generator

The thermal acid generator evaluated in this example was Nacure XC 9225,an amine salt of dinonylnaphthalene sulphonic acid sulphonic acid.

An antireflective composition was prepared by dissolving together 0.7845g of the polymer of Example 1, 0.0990 g of Powderlink 1174 crosslinker(from Cytec Industries), an acid crosslinking catalyst consisting of0.009 g of Nacure 5225 (King Industries), 0.0072 g of FC 430 surfactant(3M Corp.) and 30.96 g of proylene glycol methyl ether alcohol solvent.After dissolution, the solution was filtered through a polyproylenefilter with a 0.2 um pore size.

The filtered solution was then spin-cast on a 100 mm silicon wafer andthen baked at 175° C., to give a film thickness of about 600 angstroms.A popular commercially available “hybrid-acetal resist”, SE430 (ShinEtsu Corp.) was then spin coated on top of the antireflective film, andbaked at 90 C for 60 seconds to give a film thickness of 6000 angstroms.The resist was then exposed on a GCA 0.55 NA stepper using 248 nm lightthrough a mask to form a equal lines/spaces patterns of variousresolutions in the film. The resist film was then post-exposure baked at110 C/60 sec, and developed with 2.38% tetramethyl ammonium hydroxidedeveloper using a standard wafer-track single-puddle process.

The developed wafers were then inspected using a scanning electronmicroscope to determine the patterned fidelity. An exposure dose waschosen which gave a line/space pattern of equal size.

The SE430 resist displayed a straight resist sidewall appearance, withno undercut or footing at the resist/antireflectant interface. Resistadhesion was excellent, with features of 200 nm resolution showing notendency to tip over.

EXAMPLE 6

Improvement of Antireflectant Shelf Life Using Ionic Thermal AcidGenerator

It has been found that organic antireflectant composition undergochemical changes as they age, and that this rate of change increases athigher storage temperatures. It is desirable that the chemicalproperties of the antireflectant film do not change, as changes in filmabsorbance, refractive indices or density of crosslinking can have anegative impact on lithographic performance. One of the aging changesthat has been observed in prior antireflectants is a change in theabsorbance spectrum with storage time. While not wanting to be bound bytheory, we believe the changes to be caused by oxidation of chromophoregroups by acidic species in the antireflectant solution.

Aging phenomena was studied by storing antireflectant solutions at 40°C. to accelerate aging processes. A prior antireflectant compositioncontaining p-toluene sulphonic acid as the crosslinking catalyst wascompared to an antireflectant composition containing Nacure 5225 as thecrosslinking catalyst. Absorbance was measured at 220 nm, a peak whichwe found to correlate with absorbance changes also observed at 250 nmand even 300-400 nm. Samples of the antireflectant were removed anddiluted with THF to the same fixed concentration, prior to measurementof absorbance in a quartz cell.

Reflectant with Nacure 5225 Ionic TAG

An antireflective composition was prepared by dissolving together 0.6682g of the polymer of Example 1, 0.1177 g of the trimeric condensate ofresorcinol and diethylol-p-cresol (plasticizer), 0.0990 g of Powderlink1174 crosslinker (from Cytec Industries), an acid crosslinking catalystconsisting of 0.009 g of Nacure 5225 (King Industries), 0.0072 g of FC430 surfactant (3M Corp.) and 30.96 g of proylene glycol methyl etheralcohol solvent. After dissolution, the solution was filtered through apolyproylene filter with a 0.2 um pore size.

Reflectant with p-toluenesulphonic Acid Catalyst

An antireflective composition was prepared by dissolving together 0.6682g of the polymer of Example 1, 0.1177 g of the trimeric condensate ofresorcinol and diethylol-p-cresol (plasticizer), 0.0990 g of Powderlink1174 crosslinker (from Cytec Industries), an acid crosslinking catalystconsisting of 0.009 g of p-toluenesulphonic acid monohydrate (Aldrich),0.0072 g of FC 430 surfactant (3M Corp.) and 30.96 g of proylene glycolmethyl ether alcohol solvent. After dissolution, the solution wasfiltered through a polypropylene filter with a 0.2 um pore size.

Initial absorbance at 220 nm, time zero, after dilution into THF:

Reflectant with Nacure 5225 ionic TAG: 0.0718 absorbance units

Reflectant with p-toluenesulphonic acid catalyst: 0.0254 absorbanceunits

Absorbance at 220 nm, after 2 days aging of the reflectant at 40 C.:

Reflectant with Nacure 5225 ionic TAG: 0.0722 absorbance units

Reflectant with p-toluenesulphonic acid catalyst: 0.1655 absorbanceunits

Those results illustrates that the antireflectant compositions of thisinvention show aging related changes in the absorbance spectrum at only3% of the rate of prior antireflectants that contain an acidic catalyst.

The foregoing description of the invention is merely illustrativethereof, and it is understood that variations and modifications can beeffected without departing from the scope or spirit of the invention asset forth in the following claims.

What is claimed is:
 1. A coated substrate comprising: an antireflectivecomposition layer comprising a resin and an ionic thermal acid generatorthat comprises 1) a sulfonate having an optionally substituted phenylsubstituent or 2) a sulfonate having an optionally substitutedanthracene substituent; and a photoresist layer over the antireflectivecomposition layer.
 2. The substrate of claim 1 wherein the thermal acidgenerator comprises a sulfonate having an optionally substituted phenylsubstituent.
 3. The substrate of claim 1 wherein the thermal acidgenerator is an optionally substituted benzenesulfonate salt.
 4. Thesubstrate of claim 1 wherein the thermal acid generator comprises apara-alkylbenzenesulfonate salt.
 5. The substrate of claim 1 wherein thethermal acid generator comprises a toluenesulfonate acid amine salt. 6.The substrate of claim 1 wherein the thermal acid generator comprises asulfonate having an optionally substituted anthracene substituent. 7.The substrate of claim 1 wherein the thermal acid generator comprises anitrogen-containing cation component.
 8. The substrate of claim 1wherein the thermal acid generator comprises a counter ion that includesone or more amine groups.
 9. The substrate of claim 1 wherein thethermal acid generator comprises a cation component that is a primary,secondary or tertiary aliphatic amine.
 10. The substrate of claim 1wherein the antireflective composition layer further comprises acrosslinker component.
 11. The substrate of claim 1 wherein theantireflective composition is crosslinked.
 12. The substrate of claim 1wherein the antireflective composition layer comprises a resin havinganthracene groups.
 13. The substrate of claim 1 wherein theantireflective composition layer comprises a resin having phenyl groups.14. The substrate of claim 1 wherein the antireflective compositionlayer comprises a resin having naphthyl groups.
 15. The substrate ofclaim 1 wherein the photoresist composition is a chemically-amplifiedpositive-acting photoresist composition.
 16. The substrate of claim 1wherein the photoresist composition is a negative-acting photoresist.17. A coated substrate comprising: an antireflective composition layercomprising a resin and a polymeric ionic thermal acid generator; and aphotoresist layer over the antireflective composition layer.
 18. Thesubstrate of claim 17 wherein the thermal acid generator comprises asulfonate salt.
 19. The substrate of claim 17 wherein the thermal acidgenerator comprises a counter ion that includes one or more aminegroups.
 20. The substrate of claim 17 wherein the antireflectivecomposition layer further comprises a crosslinker component.
 21. Thesubstrate of claim 17 wherein the antireflective composition iscrosslinked.
 22. The substrate of claim 17 wherein the antireflectivecomposition layer comprises a resin having anthracene groups, phenylgroups, or naphthyl groups.
 23. The substrate of claim 17 wherein thephotoresist composition is a chemically-amplified positive-actingphotoresist composition.
 24. The substrate of claim 17 wherein thephotoresist composition is a negative-acting photoresist.
 25. A methodof forming a photoresist relief image comprising: applying over asubstrate a layer of an antireflective composition comprising a resinand an ionic thermal acid generator that comprises 1) a sulfonate havingan optionally substituted phenyl substituent or 2) a sulfonate having anoptionally substituted anthracene substituent; applying a photoresistlayer over the antireflective composition layer; and exposing anddeveloping the photoresist layer.
 26. The method of claim 25 wherein thethermal acid generator comprises a sulfonate having an optionallysubstituted phenyl substituent.
 27. The method of claim 25 wherein thethermal acid generator is an optionally substituted benzenesulfonatesalt.
 28. The method of claim 25 wherein the thermal acid generatorcomprises a para-alkylbenzenesulfonate salt.
 29. The method of claim 25wherein the thermal acid generator comprises a toluenesulfonate acidamine salt.
 30. The method of claim 25 wherein the thermal acidgenerator comprises a sulfonate having an optionally substitutedanthracene substituent.
 31. The method of claim 25 wherein the thermalacid generator comprises a nitrogen-containing cation component.
 32. Themethod of claim 25 wherein the antireflective composition is crosslinkedprior to application of the photoresist layer.
 33. The method of claim25 wherein the photoresist layer is exposed with radiation having awavelength of less than about
 250. 34. A method of forming a photoresistrelief image comprising: applying over a substrate a layer of anantireflective composition an antireflective composition layercomprising a resin and a polymeric ionic thermal acid generator;applying a photoresist layer over the antireflective composition layer;and exposing and developing the photoresist layer.
 35. The substrate ofclaim 34 wherein the thermal acid generator comprises a sulfonate salt.36. The method of claim 34 wherein the antireflective composition iscrosslinked prior to application of the photoresist layer.
 37. Themethod of claim 34 wherein the photoresist layer is exposed withradiation having a wavelength of less than about
 250. 38. Anantireflective composition for use with an overcoated photoresistcomposition, the antireflective composition comprising: 1) an aromaticresin; 2) a polymeric ionic thermal acid generator; and 3) acrosslinker.